There are so many options out there! IMO the best diet is prey model raw. It's species appropriate, doesn't have fillers & other things your pup doesn't need, keeps them healthy & their teeth sparkley clean. Plus it keeps their minds healthy as well! We did prey model raw for almost 6 months & for several reasons (Mari having issues with certain meats, the lack of variety locally & what we do have is pretty pricey except chicken & I didn't want to feed them chicken alone, plus with six I was spending at least an hour a day preparing, feeding, cleaning, etc) Anyway, I decided to switch my pups to ZiwiPeak which is a dehydrated raw, plus 1-2 days a week I give them bone in chicken to help maintain their sparkley white teeth (and it helps off-set the cost of the ZP).
It has no grains, no addatives, no dyes or fillers. It's made from meat & organ with added vitamins & minerals. It's air dried with is a biggie IMO. Cooking any ingredients of dog food basically takes out the nutrition they really need. ZiwiPeak is pretty pricey, though to feed one 5-6lbs Chi I don't think it would cost more than $25 every 6 weeks or so, so really not bad IMO since it's the best prepackaged foods on the market.
Another great dehydrated raw food is the Honest Kitchen. It's served a bit differently than the ZiwiPeak. Ziwi is basically tiny squares in jerky like form that you feed straight out of the bag (though I personally add a bit of water to it so they get some hydration when processing it). The Honest Kitchen you have to add warm water & let it set for a minimum of 5 minutes. It's served as more of a wet food but it doesn't cause the runny poo's that many wet foods do. The Honest Kitchen doesn't have as much meat as Ziwi. It also has lots of fruits & veggies in it which I don't personally feel is necessary in a canine diet and is also heated to I believe about 120*. But it's also another the best foods out there & if the Ziwi doesn't end up working out for us I'd have no problem switching to one of the grain free formula's of the Honest Kitchen.
Those are my top pics for prepackaged dog foods & of course the prey model raw is by far the best out there. But it certainly isn't for everyone & I respect that. When I first got Matilda we tried several diets from Nutro, Solid Golds Just a Wee Bit, EVO, raw & now ZiwiPeak. So far I'm happiest with the last two because I know my pups aren't getting any fillers & it's all natural & species appropriate food they are getting. Good luck in finding a food you & your pup are happy with!